went to start my car this morning and it was running on 3 cylinders, number 4 spark plug, was oiled up, i've had a mate take a quick look at it, he fixed it temporarily, and he thinks the valve guides need replacing, so is this an expensive job if done at a garage? anyone?

thing is my car has just had its pistons replaced due to melting number 4, so i am quite worried about this now, as its already cost me a fortune, and i dont want it going bang again, is the car still ok to use, i need to do another 270 miles to run it in before it goes back to msd, do you just suggest i take it back there for him to look at asap?

cheers

any advice is much appreciated

my mechanical knolwedge is very limited to say the least

so go easy on me